(a) Field of the Invention
The present invention relates to an apparatus and a method for driving a plasma display panel (PDP) and, in particular, a PDP sustain-discharge circuit.
(b) Description of the Related Art
In general, a plasma display panel (PDP) is a flat plate display for displaying characters or images using plasma generated by gas discharge. Pixels ranging from hundreds of thousands to more than millions are arranged in the form of a matrix according to the size of the PDP. PDPs are divided into direct current (DC) PDPs and alternating current (AC) PDPs according to the shape of the waveform of an applied driving voltage, and the structure of a discharge cell.
Current directly flows in discharge spaces while a voltage is applied in the DC PDP, because electrodes are exposed to the discharge spaces. Therefore, a resistor for restricting the current must be used outside of the DC PDP. On the other hand, in the case of the AC PDP, the current is restricted due to the natural formation of capacitance because a dielectric layer covers the electrodes. The AC PDP has a longer life than the DC PDP because the electrodes are protected against the shock caused by ions during discharge. A memory characteristic that is one of the important characteristics of the AC PDP is caused by the capacitance due to the dielectric layer that covers the electrodes.
In general, a method for driving the AC PDP includes a reset period, an addressing period, a sustain period, and an erase period.
The reset period is for initializing the states of the respective cells in order to smoothly perform an addressing operation on the cells. The addressing period is for selecting cells that are turned on and cells that are not turned on and for accumulating wall charges on the cells that are turned on (addressed cell). The sustain period is for performing discharge for actually displaying a picture on the addressed cells. The erase period is for reducing the wall charge of the cell and for terminating sustain-discharge.
In the AC PDP, because scan electrodes and sustain electrodes for the sustain-discharge operate as capacitive load, capacitance with respect to the scan and sustain electrodes exists. Reactive power other than power for discharge is necessary in order to apply waveforms for the sustain-discharge. A power recovering circuit for recovering and re-using the reactive power is referred to as a sustain-discharge circuit of the PDP. The sustain-discharge circuit suggested by L. F. Weber and disclosed in the U.S. Pat. Nos. 4,866,349 and 5,081,400 is the sustain-discharge circuit or the power recovery circuit of the AC PDP.
However, the conventional sustain-discharge circuit can completely operate only when the power recovery circuit charges a voltage corresponding to half of the external power in order to re-use power using the resonance of an inductor and the capacitive load (a panel capacitor). In order to uniformly sustain the potential of the power recovery capacitor, the capacitance of an external capacitor must be much larger than the capacitance of the panel capacitor. Accordingly, a structure of a driving circuit is complicated and a large amount of devices must be used in manufacturing the driving circuit.